Valveless hydraulic actuating units



VALVELESS HYDRAULIC ACTUATING UNITS Filed Oct. 23, 1965 2 Sheets-Sheet l wvavran WHITFIE LD M. P. STUART 3/ av A March 26, 1968 w. M. P. STUART 3,374,625

,VALVELESS HYDRAULIC ACTUATING UNITS Filed 001:. 23, 1965 2 Sheets-Sheet? uovg INVENTO R WHITFIELD M.P. STUART United States Patent 3,374,625 VALVELESS HYDRAULIC ACTUATIN G UNITS Whitfield M. P. Stuart, 5910 Charles St., North Burnaby, British Columbia, Canada Filed Oct. 23, 1965, Ser. No. 503,445 8 Claims. (CI. 60-52) ABSTRACT OF THE DISCLOSURE A hydraulic actuating unit particularly for use in the servo cylinder field having two independent passages therein with first and second gear means associated with said passages and operable in unison selectively to direct fluid in either direction through one passage while at the same time directing fluid through the other passage in the opposite direction.

This invention relates to valveless hydraulic actuating units and particularly to units which may be used in the servo cylinder field.

Although these actuating units may be used for different purposes, they are primarily designed as servo actuating units, and they will be described herein mainly in this connection.

This actuating unit is very simple in construction and operation, and is very sensitive and fast in operation. It directs hydraulic fluid from either end of a servo cylinder to a reservoir, and simultaneously directs fluid from said reservoir to the opposite end of the cylinder at exactly the same speed, regardless of which way the servo piston of the cylinder is moving. This unit does not require any check or control valves so that it can be instantly reversed to change the direction of movement of the servo piston. The construction is such that the unit can be mounted in the reservoir and, in fact, a wall of the reservoir can form part of the unit. As the unit simultaneously directs operating fluid to and from an open reservoir, air is constantly purged from the system.

The basic actuating unit according to this invention comprises a housing having first and second passages therein each having combined outlet-inlet openings at opposite ends thereof. Reversible gear pump means is provided in the housing for each of said passages, and suitable means interconnects the pump means so that they always operate simultaneously. The pump means can be simultaneously operated in either of two directions to move fluid in opposite directions at the same time respectively through the first and second passages. One form of the invention includes a central gear rotatably mounted in the housing near the first and second passages, and first and second side gears are rotatably mounted in the housing beside and meshing with the central gear. The first side gear meshes with the central gear in the first passage, and the second side gear meshes with said central gear in the second passage to form reversible pump means or pumps in said passages. The gears can be simultaneously rotated in either of opposite directions to move fluid through the first and second passages in opposite directions.

A further development of this invention comprises a reservoir and a closed cylinder having a servo piston slidably mounted therein. Said housing is mounted in the reservoir, and one end of each passage opens into said reservoir. Pipe means connects the opposite end of the first passage to one end of the cylinder, and pipe means connects the opposite end of the second passage to the opposite end of the cylinder. The reversible pump means in these passages can selectively direct fluid from the reservoir to either end of the cylinder and simultaneously direct fluid from the other end of the cylinder to the reservoir.

3,374,625 Patented Mar. 26, 1968 An example of this invention is illustrated in the accompanying drawings, in which:

FIGURE 1 is a diagrammatic elevation, partly in section, of one form of hydraulic actuating unit,

FIGURE 2 is a side elevation of another form of hydraulic actuating unit,

FIGURE 3 is a plan view of the unit of FIGURE 2,

FIGURE 4 is a horizontal section taken on the line 44 of FIGURE 2,

FIGURE 5 is a cross section taken on the line 55 of FIGURE 4,

FIGURE 6 is fragmentary sectional view taken on the line 6-6 of FIGURE 3,

FIGURE 7 is a view similar to FIGURE 1 of another alternative form of hydraulic actuating unit,

FIGURE 8 is an enlarged vertical cross section through the unit of FIGURE 7,

FIGURE 9 is a horizontal section taken on the line 9-9 of FIGURE 8, and

FIGURE 10 is a horizontal section taken on the line 1010 of FIGURE 7.

Referring to FIGURES l to 6 of the drawings, 10 is a complete hydraulic actuating mechanism or unit including a preferred form of basic actuating unit 12 mounted in a reservoir 13 having a hydraulic fluid 14 therein. The mechanism or unit 10 includes a servo cylinder 16 having a piston 17 slidably mounted therein with rods 19 and 20 connected to said piston and slidably extending through ends 22 and 23 of the cylinder. Pipes 25 and 26 extend from unit 12 to cylinder 16 respectively adjacent ends 22 and 23 thereof.

Unit 12 includes a housing or block 30' having a substantially flat surface 31. Spaced passages or grooves 33 and 34 are formed in surface 31 and open outwardly through side 35 of housing 30. Passages 33 and 34 have inlet-outlet openings 37 and 38 opening into reservoir 13. In this example, passages 33 and 34 are horizontal, and have vertical sections 40 and 41 which extend upwardly to inlet-outlet openings 43 and 44 opening out from the top of housing or block 30'. Pipes 25 and 26 are suitably connected to passage openings 43 and 44 respectively.

A substantially cylindrical central chamber 48 is formed in surface 31 of block 30' between passages 33 and 34- and opens thereinto. A central gear 50 rotatably fits in chamber 48 and extends laterally into passages 33 and 34. Substantially circular side chambers 52 and 53 are formed in block surface 31 on the sides of passages 33 and 34 remote from chamber 48. Side gears 55 and 56 rotatably fit in chambers 52 and 53 respectively and project into passages 33 and 34 to mesh therein with central gear 50.

Power means is connected to one of said gears to rotate the latter and the other gears in opposite directions. In this example, shaft 59 extends upwardly from central gear 50 and out through the top of housing 30, said shaft being operatively connected to a suitable source of power, such as a reversible hydraulic or electric motor 60 supported on the top of housing 30 by a bracket 61. Gears 55 and 56 have stub shafts 63 and 64 projecting upwardly therefrom and journalled in housing block 30.

In this example, a plate 68 is mounted on block surface 31 by suitable means, such as bolts 69, said plate being secured to the bottom wall of reservoir 13 in any convenient manner. However, plate 68 can be omitted, in which case, housing block 30 is mounted directly on the bottom wall of the reservoir so that said wall acts as a cover for passages 33 and 34-, and chambers 50, 52 and 53.

The operation of the hydraulic actuating mechanism 10 is quite simple. When motor 60 is operated to turn gear 50 in one direction, for example, in the direction of arrow 72 in FIGURE 4, said central gear and side gear 56 draw hydraulic fluid 14 from reservoir 13 into passage 34, forcing said fluid from said passage through pipe 26 into end 23 of cylinder 16 to move servo piston 17 to the left with reference to FIGURE 1. At the same time, central gear 57 and side gear 55 draw fluid from the end 22 of cylinder 16 through pipe 25 and passage 33 to discharge the fluid into the reservoir. When motor 60 is reversed, this action is reversed and fluid from the reservoir moves piston 17 to the right in FIGURE 1, while fluid is directed through passage 34 back into the reservoir. This apparatus is very sensitive and fast since unit 12 pumps fluid into one end of the servo cylinder and out of the opposite end thereof at exactly the same speed, regardless of which way the piston is being moved. This is a result of the fact that gears 55 and 56 are of the same size, and gears 50 and 55 form a gear pump in passage 33 which is exactly the same as .a gear pump in passage 34 formed by gears 50 and 56. As the combination gear pump blocks the flow of fluid through passages 33 and 34 when it is not in operation, it eliminates the necessity of check or control valves. Thus, when the direction of rotation of central gear 50 is reversed, there is an instant reversal of the movement of piston 17. Furthermore, motor 60 can be turned in either of the two opposite directions to move fluid in either direction through passages 33 and 34 since there are no check valves therein.

Actuating unit 12 is very simple, and it is made up mainly of housing or block 30 having passages and chambers formed in the surface 31 thereof, said passages and chambers being enclosed either by plate 68 or by the bottom wall of reservoir 13. For some purposes, it is desirable to mount unit 12 in reservoir 13, but where this is not desirable, the unit can be mounted outside the reservoir, in which case, openings 37 and 38 of passages 33 and 34 would be connected by pipes or a common pipe to the reservoir.

FIGURES 7 to illustrate an alternative form of actuating unit 80 mounted on the bottom wall of a fluid reservoir 81. Unit 80 includes a housing or block 83 having .a lower surface 84 in which is formed a groove or passage 85 which has an inlet-outlet opening 86 at one end opening outwardly from a side of the block. The opposite end of passage 85 has an inlet-outlet opening 89 opening out from a side of the block and to which a pipe 90 is connected, said pipe extending to one end of a hydraulic cylinder, not shown. Gears 92 and 93 rotatably fit in chambers 94 and 95 formed in block 83 on opposite sides of passage 85, said gears meshing with each other in the passage, as shown in FIGURE 9, and forming a reversible gear pump 96 for moving fluid through said passage. A plate 99 is secured to the bottom of block 83 in a convenient manner, such as by bolts 100.

A second block or housing 103 has an upper surface 104 over which plate 99 lies, said plate being secured to block 103 by bolts 100, which also secure unit 80 to the bottom wall of reservoir 81.

A passage. or groove 106 is formed in the upper surface of block 103 and has an inlet-outlet opening 107 at one end opening out from a side of the block. Passage 106 has an opposite end forming an inlet-outlet opening 108 which opens out from another side of block 103, and to which a pipe 110 is connected, said pipe extending to the opposite end of the cylinder to which pipe 90 is connected.

Chambers 112 and 113 are formed in block 103 on opposite sides of passage 106, and gears 115 and 116 rotatably fit in these chambers and mesh with each other in passage 106 to form a reversible gear pump 118 adapted to move fluid in either direction along passage 106. Gears 93 and 116 of pumps 96 and 118 are mounted one above the other and are fixedly mounted on a common drive shaft 122 which extends through blocks 83 and 103, and plate 99. This shaft is operatively connected "to .a reversible motor 124 mounted on top of block 83 by a suitable bracket 125.

Blocks 83 and 103 and plate 99 form a housing or block containing passages 85 and 106, and reversible pumps 96 and 118.

Unit operates in the same manner as unit 12, the only difference between the two units being that the gear pumps of unit 12 have one gear common to both of them, whereas pumps 96 and 118 of unit 80 have a common drive shaft for gears 93 and 116. Pumps 96 and 118 are identical so that when motor 124 is turning in one direction, fluid is drawn from reservoir 81 into one passage of the unit and directed to one end of the servo cylinder, while fluid is simultaneously and at the same rate withdrawn from the opposite end of said cylinder and directed through the other passage of the unit into the reservoir. For example, when fluid is drawn from the reservoir into passage by pump 96, at the same time fluid is drawn from the cylinder into passage 106 by pump 118 to be discharged into the reservoir. This action is reversed when motor 124 operates in the opposite direction.

In each of the illustrated forms of'the invention, fluid is simultaneously moved in one direction through one of the passages of the actuating unit and simultaneously moved in the opposite direction through the other passage of said unit at exactly the same speed since the fluid is moved in both'passages by identical gear pumps operating at exactly the same speed. In addition to this, there is a gear pump in each of the passages of each unit so that it prevents the movement of liquid through its passage when the gear pumps are not operating, thereby eliminating the necessity of check or control valves for controlling the flow of fluid. Each actuating unit can be mounted within a reservoir, or the passages thereof can be connected to the reservoir by pipes. In' either case, when the reservoir is open to atmosphere, the system controlled by the actuating unit is constantly purged of air since the unit is constantly directing fluid into and out of said reservoir.

What I claim as my invention is:

1. A hydraulic actuating unit comprising a housing block having an outer surface, grooves formed in said surface forming first and second passages opening outwardly therefrom, a central substantially circular chamber formed in said block surface between the passage grooves, a central gear rotatably fitting in the central chamber and extending into said grooves, first and second side substantially circular chambers formed in the block surface near the grooves on side thereof remote from the central chamber, first and second side gears rotatably fitting in the first and second side chambers respectively and projecting into the first and second grooves to mesh therein with the central gear, a plate on said block surface covering the grooves and chambers formed therein, said side gears forming with the central gear reversible pumps in the first and second passages, whereby rotation of said gears in either of opposite directions can cause fluid to move through the first and second passages in opposite directions.

2. A hydraulic actuating unit comprising a reservoir, a closed cylinder, a servo piston slidably mounted in the cylinder, a housing mounted in the reservoir, first and second passages in the housing each having one end opening into the reservoir, pipe means connecting the opposite end of the first passage to one end of the cylinder, pipe means connecting the opposite end of the second passage to the opposite end of the cylinder, a central gear rotatably mounted in the housing near the passage therein, and first and second side gears rotatably mounted in the housing beside and meshing with the central gear, said first side gear meshing with the central gear in the first passage and the second side gear meshing with said central gear in the second passage to form reversible pumps in said passages for selectively directing fluid from the reservoir to either end of the cylinder and simultaneously directing fluid from the other, end of the cylinder to the reservoir.

3. A hydraulic actuating unit as claimed in claim 2 including power means operatively connected to one of said gears to rotate said one gear in opposite directions.

4. A hydraulic actuating unit comprising a reservoir, a closed cylinder, a servo piston slidably mounted in the cylinder, a housing block mounted in the reservoir on a wall thereof and having an outer surface normally bearing against said wall, grooves formed in said surfaceforming first and second passages having ends opening outwardly therefrom into the reservoir, pipe means connecting the opposite end of the first passage to one end of the cylinder, pipe means connecting the opposite end of the second passage to the opposite end of the cylinder, a central substantially circular chamber formed in said block surface between the passage grooves, a central gear rotatably fitting in the central chamber and extending into said grooves, first and second side substantially circular chambers formed in the block surface near the grooves on sides thereof remote from the central chamber, first and second side gears rotatably fitting in the first and second side chambers respectively and projecting into the first and second grooves to mesh therein with the central gear, said side gears forming with the central gear reversible pumps in said passages for selectively directing fluid from the reservoir to either end of the cylinder and simultaneously directing fluid from the other end of the cylinder to the reservoir.

5. A hydraulic actuating unit comprising a housing, first and second passages in the housing each having inletoutlet openings at opposite ends thereof, said passages being spaced from each other, a first pair of gears in the housing and meshing in the first passage to form a first gear pump, a second pair of gears in the housing the same as and substantially parallel with the first pair of gears and meshing in the second passage to form a second gear pump, and a drive shaft extending through the housing, one gear of each pump fixedly mounted on the drive shaft, said shaft on being rotated turning the gears therein simultaneously to operate the first and second gear pumps selectively to move fluid in either direction through the first passage and at the same time in the opposite direction through the second passage.

6. A hydraulic actuating unit as claimed in claim 5 including power means operatively connected to the drive shaft to rotate said shaft in opposite directions.

7. A hydraulic actuating unit comprising a housing, first and second passages in the housing each having inletoutlet openings at opposite ends thereof, said passages being spaced from each other, a first pair of gears in the housing and meshing in the first passage to form a first gear pump, a second pair of gears in the housing the same as and substantially parallel with the first pair of gears and meshing in the second passage to form a second gear pump, a drive shaft extending through the housing, one gear of each pump being fixedly mounted on the drive shaft, a reservoir, a closed cylinder, and a servo piston slidably mounted in the cylinder, one end of each passage being in communication with the reservoir, the opposite end of the first passage being in communication with one end of the cylinder, and the opposite end of the second passage being in communication with the opposite end of said cylinder.

8. A hydraulic actuating unit comprising a reservoir, a closed cylinder, a servo piston slidably mounted in the cylinder, a housing mounted in the reservoir, first and second passages in the housing each having one end opening into the reservoir, pipe means connecting the opposite end of the first passage to one end of the cylinder, pipe means connecting the opposite end of the second passage to the opposite end of the cylinder, said passages being spaced from each other, a first pair of gears in the housing and meshing in the first passage to form a first gear pump, a second pair of gears in the housing the same as and substantially parallel with the first pair of gears and meshing in the second passage to form a second gear pump, and a drive shaft extending through the housing, one gear of each pump being fixedly mounted on the drive shaft, said shaft on being rotated turning the gears there, on selectively to direct fluid from the reservoir to either end of the cylinder and simultaneously directing fluid from the other end of the cylinder to the reservoir.

References Cited UNITED STATES PATENTS 1,927,580 9/1933 Wisner -52 X 1,993,612 3/1935 Lum 6052 X 2,679,727 6/1954 McLeod 6052 FOREIGN PATENTS 866,161 4/ 1941 France.

511,298 8/ 1939 Great Britain.

628,091 11/1961 Italy.

EDGAR W. GEOGHEGAN, Primary Examiner- 

